JP5953784B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a fixing device that thermally fixes a developer image on a recording sheet and a control device that controls the fixing device.

2. Description of the Related Art Conventionally, an image forming apparatus includes a heating member that is heated by a heat source supplied with electric power, a temperature sensor that detects the temperature of the heating member, and a control device that controls the heat source based on the temperature detected by the temperature sensor. It is known (see Patent Document 1).
This control device is configured to control the timing of supplying electric power to the heat source (turning on the heat source) in accordance with the degree of warming around the heating member.

  In other words, when receiving a print command, this control device supplies power to the heat source at an early timing when the temperature sensor detects a low temperature, and supplies power to the heat source when the temperature sensor detects a high temperature. It is comprised so that the timing to perform may be delayed.

JP 2002-169411 A

  However, even if the temperature detected by the temperature sensor is high, if the timing for supplying power to the heat source is delayed, a large amount of power must be supplied to the heat source, and the temperature of the heating member exceeds the fixing temperature. In other words, so-called overshoot may occur.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of suppressing overshoot of the temperature of a heating member.

In order to solve the above problems, an image forming apparatus according to the present invention detects a heating member heated by a heat source, a backup member for sandwiching a recording sheet between the heating members, and a temperature of the heating member. A fixing device having a temperature sensor; and a control device for controlling the heat source.
The control device controls the heat source so that the temperature of the heating member rises with a gradient equal to or greater than a predetermined value when the temperature of the heating member when receiving a print command is in a low temperature state lower than a predetermined temperature. When the normal mode is executed and the temperature of the heating member when the print command is received is in a high temperature state that is equal to or higher than a predetermined temperature, the temperature of the heating member rises with a smaller gradient than in the normal mode. Then, after executing the preheating mode for controlling the heat source, the mode is shifted to the normal mode.

  Here, “when a print command is received” indicates the moment when the print command is received or a time zone in the vicinity thereof.

  According to this configuration, when the temperature when the print command is received is in a high temperature state, the temperature of the heating member can be brought close to the fixing temperature by the preheating mode before entering the normal mode. Compared with control in which the heat source is turned off for a predetermined waiting time and turned on after the predetermined waiting time, the gradient of the temperature gradient when the fixing temperature is reached is reduced, and overshoot can be suppressed.

  For example, in the preheating mode, the control device described above may turn on the heat source for a predetermined time after receiving the print command, turn it off, and then shift to the normal mode. Alternatively, the control device described above may make the output of the heat source smaller than the maximum value in the normal mode in the preheating mode.

  In the above-described configuration, a polygon motor for driving a polygon mirror provided in an exposure apparatus that exposes the photosensitive member, and a main motor that rotates at least one of the backup member and the heating member may be provided. At this time, the control device drives the polygon motor after driving the main motor in the low temperature state, and drives the main motor after driving the polygon motor in the high temperature state. It is desirable to shift from the preheating mode to the normal mode when the main motor is driven.

  According to this, since a motor that consumes a large amount of power at the start of driving is not driven at the same time, power consumption can be suppressed. Also, when the main motor is in a high temperature state, it is in a preheating mode before the main motor is driven, so that the nip portion between the non-rotating backup member and the heating member is prevented from being damaged by heat from the heat source. be able to.

  According to the present invention, overshooting of the temperature of the heating member can be suppressed.

1 is a cross-sectional view illustrating a laser printer according to an embodiment of the present invention. 2 is a cross-sectional view illustrating a fixing device. It is a perspective view which shows a nip plate and a temperature sensor. It is a flowchart which shows operation | movement of a control apparatus. It is a time chart which shows the relationship between the operation | movement of a halogen lamp and each motor at the time of low temperature, and the temperature of a nip plate. It is a time chart which shows the relationship between the operation | movement of a halogen lamp and each motor at the time of high temperature, and the temperature of a nip plate. It is a time chart which shows the modification of preheating mode.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, a schematic configuration of a laser printer 1 as an example of an image forming apparatus according to an embodiment of the present invention will be briefly described, and then a fixing device and a control device will be described in detail.

  In the following description, the direction will be described with reference to the user who uses the laser printer 1. That is, the left side in FIG. 1 is “front”, the right side is “rear”, the back side is “left”, and the front side is “right”. Also, the vertical direction in FIG.

<Schematic configuration of laser printer>
As shown in FIG. 1, a laser printer 1 includes a main body housing 2 that feeds a sheet S as an example of a recording sheet, an exposure device 4, and a toner image (developer) on the sheet S. And a fixing device 100 that thermally fixes the toner image on the paper S.

  The paper feed unit 3 is provided at a lower portion in the main body housing 2 and mainly includes a paper feed tray 31, a paper pressing plate 32, and a paper feed mechanism 33. The paper S stored in the paper feed tray 31 is moved upward by the paper pressing plate 32 and supplied toward the process cartridge 5 (between the photosensitive drum 61 and the transfer roller 63) by the paper feed mechanism 33.

  The exposure device 4 is disposed in the upper part of the main body housing 2 and rotationally drives the laser light emitting unit (not shown), the polygon mirror 41, the lenses 42 and 43, the reflecting mirrors 44, 45, and 46, and the polygon mirror 41. And a polygon motor 47 for this purpose. In the exposure device 4, laser light (see the chain line) based on image data emitted from the laser light emitting unit passes or reflects in the order of the polygon mirror 41, the lens 42, the reflecting mirrors 44 and 45, the lens 43, and the reflecting mirror 46. The surface of the photosensitive drum 61 is exposed by being scanned at high speed on the surface of the photosensitive drum 61.

  The process cartridge 5 is disposed below the exposure apparatus 4 and is detachably mounted on the main body housing 2 through an opening formed when the front cover 21 provided on the main body housing 2 is opened. Yes. The process cartridge 5 includes a drum unit 6 and a developing unit 7.

  The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is configured to be detachably attached to the drum unit 6, and includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a toner that contains toner (developer). The container mainly includes a container 74 and an agitator 75 that stirs the toner in the toner container 74.

  In the process cartridge 5, the surface of the photosensitive drum 61 is uniformly charged by the charger 62 and then exposed by high-speed scanning of the laser light from the exposure device 4, whereby an image is formed on the photosensitive drum 61. An electrostatic latent image based on the data is formed. Further, the toner in the toner container 74 is supplied to the developing roller 71 via the supply roller 72 and enters between the developing roller 71 and the layer thickness regulating blade 73 to form a thin layer of a certain thickness on the developing roller 71. It is carried on.

  The toner carried on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 61. Thereafter, the sheet S is conveyed between the photosensitive drum 61 and the transfer roller 63 so that the toner image on the photosensitive drum 61 is transferred onto the sheet S.

  The fixing device 100 is provided behind the process cartridge 5. The toner image transferred onto the sheet S is thermally fixed onto the sheet S by passing through the fixing device 100. Thereafter, the paper S is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

<Detailed configuration of fixing device>
As shown in FIG. 2, the fixing device 100 includes a fixing belt 110 and a nip plate 130 as an example of a heating member, a halogen lamp 120 as an example of a heat source, a pressure roller 140 as an example of a backup member, and a reflection. A plate 150 and a stay 160 are provided.

  The fixing belt 110 is an endless (cylindrical) stainless steel belt having heat resistance and flexibility, and a halogen lamp 120, a nip plate 130, a reflecting plate 150, and a stay 160 are provided therein. ing.

  The halogen lamp 120 is a member that emits radiant heat to heat the toner on the sheet S by heating the nip plate 130 and the fixing belt 110 (nip portion N), and is spaced from the inner surface of the nip plate 130 by a predetermined interval. Has been placed.

  The nip plate 130 is a plate-like member that receives radiant heat from the halogen lamp 120, and is arranged so that the lower surface thereof is in sliding contact with the inner peripheral surface of the fixing belt 110. In the present embodiment, the nip plate 130 is made of metal, and is formed, for example, by bending an aluminum plate or the like having a higher thermal conductivity than a steel stay 160 described later. If the nip plate 130 is made of aluminum, the thermal conductivity of the nip plate 130 can be improved.

  As shown in FIGS. 2 and 3, the nip plate 130 includes a plate-like portion 131, a front bent portion 132, a rear bent portion 133, and three detected portions 134.

  The plate-like portion 131 is a long plate-like member that is orthogonal to the vertical direction and that is long in the left-right direction. The plate-like portion 131 is sandwiched between the pressure belt 140 and the fixing belt 110 in a vertical direction. The nip portion N is formed. The plate-like portion 131 is arranged below the halogen lamp 120 and transmits heat from the halogen lamp 120 to the toner on the paper S via the fixing belt 110.

  Note that the inner surface (upper surface) of the plate-like portion 131 may be painted black or provided with a heat absorbing member. According to this, the radiant heat from the halogen lamp 120 can be efficiently absorbed.

  The front bent portion 132 is formed so as to be bent in a substantially arc shape upward from the front end side (upstream side in a predetermined direction) of the plate-like portion 131, and is disposed so as to face the halogen lamp 120. As a result, the front bent portion 132 is directly heated by the halogen lamp 120, so the sheet S before entering the nip portion N can be preheated (preheated) by the front bent portion 132, and the heat fixing property is improved. It is possible.

  The rear bent portion 133 is formed to extend upward (inward in the radial direction of the fixing belt 110) from the rear edge of the plate-like portion 131. Specifically, the rear bent portion 133 is formed so as to extend from one end side to the other end side in the left-right direction among the rear end edges of the plate-like portion 131. Thereby, the rear side bent portion 133 effectively suppresses the lubricant G adhering to the inner peripheral surface of the fixing belt 110 from flowing into the upper surface of the plate-like portion 131 (the surface on which black coating or the like is applied). Therefore, it is possible to suppress a reduction in heating efficiency of the nip plate 130.

  The three detected portions 134A, 134B, and 134C are portions where temperatures are detected by the side thermistor 400A, the thermostat 400B, and the center thermistor 400C, respectively. The three detected parts 134A, 134B, and 134C are formed so as to extend from a part of the upper end edge 133A of the rear bent part 133 to the rear side. Specifically, two detected portions 134B and 134C are disposed at a substantially central portion of the rear bent portion 133 extending in the left-right direction, and one detected portion 134A is disposed at one end portion on the outer side in the left-right direction.

Further, as shown in FIG. 3, the detected parts 134B and 134C are arranged within the minimum sheet passing range PR in the left-right direction, and the detected part 134A is arranged outside the minimum sheet passing range PR in the left-right direction. ing. Here, the minimum sheet passing range PR refers to a sheet passing range having a minimum width in the left-right direction among the sheets that can be used in the laser printer 1.
Here, the side thermistor 400A and the center thermistor 400C are temperature sensors for transmitting the detected temperature to the control device 510, and the thermostat 400B mechanically transfers to the halogen lamp 120 when the detected temperature exceeds a predetermined temperature. This is a thermal switch that cuts off the power supply.

The side thermistor 400A may be a contact type thermistor that detects the temperature of the detected part 134A by contacting the detected part 134A, or the side thermistor 400A does not contact the detected part 134A. A non-contact thermistor that detects the temperature may be used.
Similarly, the center thermistor 400C may be a contact type thermistor that detects the temperature of the detected part 134C by contacting the detected part 134C, or the detected part 134C without contacting the detected part 134C. It may be a non-contact thermistor that detects the temperature.

  The pressure roller 140 is a member that forms a nip portion N with the fixing belt 110 by sandwiching the fixing belt 110 with the nip plate 130, and is disposed below the nip plate 130. In order to form the nip portion N, one of the nip plate 130 and the pressure roller 140 is urged toward the other. The pressure roller 140 is configured to be rotated by a driving force transmitted from a main motor 500 (see FIG. 1) provided in the main body casing 2, and between the pressure roller 140 and the nip plate 130. By rotating with the fixing belt 110 and the paper S sandwiched therebetween, the paper S is rotated with the fixing belt 110 and conveyed backward.

  The reflection plate 150 is a member that reflects the radiant heat from the halogen lamp 120 toward the nip plate 130, and is disposed at a predetermined interval from the halogen lamp 120 so as to surround the halogen lamp 120 inside the fixing belt 110. ing. The reflecting plate 150 is formed by curving an aluminum plate or the like in a U shape in a sectional view, for example, having high infrared and far-infrared reflectance.

  The stay 160 is a member that receives a load from the pressure roller 140 by supporting the nip plate 130 via the reflection plate 150, and is arranged so as to surround the halogen lamp 120 and the reflection plate 150 inside the fixing belt 110. ing. Note that the load referred to here is the reaction force of the force with which the nip plate 130 biases the pressure roller 140 in the configuration in which the nip plate 130 biases the pressure roller 140. Such a stay 160 has relatively high rigidity, for example, is formed by bending a steel plate or the like.

  The main motor 500 for driving the halogen lamp 120 of the fixing device 100 configured as described above, the pressure roller 140, and the like, and the polygon motor 47 described above are controlled by the control device 510 shown in FIG. It is like that. The main motor 500 supplies driving force to the pressure roller 140 via a gear mechanism (not shown) and also applies driving force to the developing roller 71, the supply roller 72, and the agitator 75 via a gear mechanism (not shown). It is configured to supply. That is, when the main motor 500 is driven, the pressure roller 140, the developing roller 71, the supply roller 72, and the agitator 75 are rotated simultaneously.

<Control device>
Next, the control device 510 will be described in detail.
As shown in FIG. 1, the control device 510 includes, for example, a CPU, a RAM, a ROM, and an input / output circuit. The input from the center thermistor 400C and the side thermistor 400A described above, the contents of the print command, and the ROM The halogen lamp 120, the main motor 500, and the polygon motor 47 are controlled by performing arithmetic processing based on stored programs and data. The temperature sensor used in the following control may be either the side thermistor 400A or the center thermistor 400C, but in this embodiment, the temperature sensor used in the following control is the center thermistor 400C.

  The control device 510 turns on the halogen lamp 120 when receiving the print command, and controls the halogen lamp 120, the main motor 500, and the polygon motor 47 according to the temperature of the nip plate 130 at the time when the print command is received. Is configured to change.

  When the laser printer 1 is turned on (when the power is on), the controller 510 basically turns off the halogen lamp 120 until a print command is received during the standby period. That is, the laser printer 1 employs a so-called on-demand fixing method. Here, the standby period is a period excluding the initial error check period when the power is turned on, and indicates a period during which the print command can be accepted.

  Specifically, the control device 510 performs control according to the flowchart shown in FIG. 4 while the laser printer 1 is powered on. In this control, control device 510 first determines whether a print command has been received (S1).

  In step S1, control device 510 terminates the present control as it is without receiving a print command (No), and keeps halogen lamp 120 off, and if it receives a print command (Yes). The temperature of the nip plate 130 is acquired from the center thermistor 400C (S2). After step S2, control device 510 determines whether or not the temperature of nip plate 130 at the time of receiving the print command is lower than predetermined temperature TH1 (S3).

  Here, the “predetermined temperature TH1” is a threshold value for distinguishing between a low temperature state in which the temperature in the laser printer 1 is low to some extent or a high temperature state higher than the low temperature state, and can be set as appropriate through experiments or the like. In the present embodiment, the predetermined temperature TH1 is 152 ° C.

  In step S3, when the temperature of the nip plate 130 is lower than the predetermined temperature TH1, that is, when the temperature is low (Yes), the controller 510 causes the temperature of the nip plate 130 to be equal to or higher than the predetermined value G1 (see FIG. 5). A normal mode for controlling the halogen lamp 120 so as to rise at a gradient is executed (S4), and the main motor 500 is driven (S5). The “predetermined value G1” can be set as appropriate through experiments or the like. In the present embodiment, G1 = 20 ° C./sec.

  Here, the normal mode refers to a mode in which the temperature of the halogen lamp 120 is raised to the fixing temperature TH2 (see FIG. 5) based on the temperature detected by the center thermistor 400C and maintained at the fixing temperature TH2. In FIGS. 5 and 6, for the sake of convenience, the output of the halogen lamp 120 in the normal mode is shown as a constant value. However, in practice, the output changes as appropriate based on the temperature of the center thermistor 400C.

  After step S5, control device 510 determines whether or not first time T1 has elapsed since receiving the print command (S6). Here, the “first time T1” is appropriately set based on the time from when the driving of the main motor 500 is started until it is stabilized, that is, the time until the large power required at the start of driving becomes unnecessary. Is done.

  In step S6, when the first time T1 has elapsed (Yes), the control device 510 drives the polygon motor 47 (S7).

  In step S3, when the temperature of the nip plate 130 is equal to or higher than the predetermined temperature TH1, that is, when it is in a high temperature state (No), the control device 510 determines that the temperature of the nip plate 130 (the detected temperature of the center thermistor 400C) is normal. A preheat mode (see FIG. 6) for controlling the halogen lamp 120 so as to rise at a gradient smaller than the gradient during the mode (the gradient of the predetermined value G1) is executed (S8), and the polygon motor 47 is driven. (S9).

  In the present embodiment, the “preheating mode” refers to a mode in which the halogen lamp 120 is turned on for a predetermined time TA after the printing command is received and then turned off as shown in FIG. In the present embodiment, the output of the halogen lamp 120 in the preheating mode is made smaller than the maximum value in the normal mode. Specifically, in this preheating mode, control device 510 turns on halogen lamp 120 for 0.6 seconds with a duty ratio of 33%.

  Returning to FIG. 4, the continuation of the control will be described. After step S9, control device 510 determines whether or not second time T2 has elapsed after receiving the print command (S10). Here, the “second time T2” is appropriately determined based on the time from when the driving of the polygon motor 47 is started until it is stabilized, that is, the time until the large power required at the start of driving becomes unnecessary. It is a set value, and is set to a time longer than the first time T1.

  In step S10, when the second time T2 has passed (Yes), the control device 510 drives the main motor 500 (S11) and shifts from the preheating mode to the normal mode (S12). After step S12 or after step S7, control device 510 determines whether or not printing control has ended (S13). If printing control has not ended (No), processing in step S13 is performed. When the print control is finished (Yes), this control is finished.

  Next, a specific example of control at a low temperature and a high temperature by the control device 510 will be described with reference to FIGS.

  As shown in FIG. 5, when the control device 510 receives a print command (time t1) and determines that the temperature is low (less than a predetermined temperature TH1), the control device 510 turns on the halogen lamp 120 to turn on the normal mode. Then, the control is started and the main motor 500 is driven. As a result, when the temperature is low, the temperature of the nip plate 130 rises with a gradient equal to or higher than the predetermined value G1 in the normal mode, so that the temperature of the nip plate 130 can be quickly raised to the fixing temperature TH2.

  Further, when the temperature is low, the main motor 500 is driven before the polygon motor 47 so that the pressure roller 140 can be rotated simultaneously with the halogen lamp 120 being turned on. It can be suppressed that the temperature of the nip portion N between 140 and the fixing belt 110 becomes too high and the fixing belt 110 and the like are damaged.

  Then, control device 510 drives polygon motor 47 (time t2) when first time T1 elapses from when the print command is received (time t1). In other words, since the polygon motor 47 is driven after the large electric power required at the start of driving of the main motor 500 is not required, the time is shorter than in the case where the main motor 500 and the polygon motor 47 are driven simultaneously. It can prevent consuming large electric power.

  As shown in FIG. 6, when the control device 510 receives a print command (time t3) and determines that it is in a high temperature state (predetermined temperature TH1 or more), it turns on the halogen lamp 120 and turns on the preheating mode. Then, the control is started and the polygon motor 47 is driven. In the preheating mode, the halogen lamp 120 is turned off (time t4) after a predetermined time TA from when the print command is received (time t3).

  Thereby, in the high temperature state, the temperature of the nip plate 130 rises with a gradient smaller than the gradient of the predetermined value G1 in the preheating mode, so that the temperature of the nip plate 130 can be brought close to the fixing temperature TH2 and the main motor 500 Overheating of the nip portion N due to the stop can be suppressed.

  Then, when the second time T2 has elapsed from when the printing command is received (time t3), control device 510 turns on halogen lamp 120 again to control in the normal mode and drives main motor 500 (time t5). ). As described above, the timing for relighting the halogen lamp 120 and the timing for starting the driving of the main motor 500 are simultaneously performed, so that the main motor 500 is stopped as compared with the case where the main motor is driven with a delay from the relighting of the halogen lamp, for example. The overheating of the nip portion N due to can be further suppressed.

According to the above, the following effects can be obtained in the present embodiment.
When the temperature at the time of receiving the print command (time t3) is a high temperature state, the temperature of the nip plate 130 can be brought close to the fixing temperature TH2 by the preheating mode before entering the normal mode. Compared with the control as shown in FIG. 5, the inclination of the temperature gradient when reaching the fixing temperature TH2 is reduced, and overshoot can be suppressed. Here, the control indicated by the broken line indicates control in which the halogen lamp 120 is turned off for a predetermined waiting time (T2) from when the print command is received at a high temperature (time t3) and turned on after the predetermined waiting time.

In addition, this invention is not limited to the said embodiment, It can utilize with various forms so that it may illustrate below.
In the above embodiment, in the preheating mode, the halogen lamp 120 is turned on for a predetermined time TA and then turned off until the normal mode is entered. However, the present invention is not limited to this. For example, as shown in FIG. 7, in the preheating mode, if the output of the halogen lamp is made smaller than the maximum value in the normal mode, the halogen lamp may be kept ON during the preheating mode (between times t6 and t7). .

  In the embodiment, the control device 510 is configured to turn off the halogen lamp 120 during the standby period. However, the detected temperature of the center thermistor 400C is lower than the fixing temperature TH2 during the standby period. The halogen lamp 120 may be controlled.

  In the above embodiment, the present invention is applied to the laser printer 1. However, the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as a copying machine and a multifunction machine.

  In the embodiment, the halogen lamp 120 is illustrated as an example of the heat source. However, the present invention is not limited to this, and may be, for example, a heating resistor or an IH heat source. Here, the IH heat source does not generate heat by itself, but generates heat from a roller or a metal belt by an electromagnetic induction heating method.

  In the above-described embodiment, the fixing belt 110 and the nip plate 130 are illustrated as an example of the heating member. However, the present invention is not limited to this, and for example, a heating roller that is a metal tube thicker than the fixing belt 110 may be used. Good.

  In the embodiment, the pressure roller 140 (backup member) is rotated by the main motor 500, but the present invention is not limited to this, and the motor may rotate at least one of the backup member and the heating member. For example, when the heating member is a heating roller, the heating roller may be driven by a motor.

  In the embodiment, the paper S such as a thick paper, a postcard, and a thin paper is used as an example of the recording sheet. However, the present invention is not limited to this, and may be an OHP sheet, for example.

  In the embodiment, the pressure roller 140 is illustrated as an example of the backup member, but the present invention is not limited to this, and may be a belt-shaped pressure member, for example.

  The control device that controls the heat source and the control device that controls each motor may be separate or may be configured as one control device.

  In the above embodiment, the photosensitive drum 61 is illustrated as an example of the photosensitive member, but the present invention is not limited to this, and for example, a belt-shaped photosensitive member may be adopted.

DESCRIPTION OF SYMBOLS 1 Laser printer 100 Fixing device 110 Fixing belt 120 Halogen lamp 130 Nip plate 140 Pressure roller 400 Temperature sensor 510 Control device S Paper TH1 Predetermined temperature

Claims (4)

A fixing device having a heating member heated by a heat source, a backup member for sandwiching a recording sheet between the heating member, and a temperature sensor for detecting the temperature of the heating member;
A polygon motor for driving a polygon mirror provided in an exposure apparatus that exposes a photoconductor;
A main motor that rotates at least one of the backup member and the heating member;
An image forming apparatus comprising: a control device that controls the heat source;
The controller is
When the temperature of the heating member at the time of receiving a print command is in a low temperature state lower than a predetermined temperature, a normal mode is executed to control the heat source so that the temperature of the heating member rises with a gradient of a predetermined value or more. And
Preheating for controlling the heat source so that the temperature of the heating member rises with a smaller gradient than that in the normal mode when the temperature of the heating member is higher than a predetermined temperature when receiving a print command. After executing the mode, transition to the normal mode ,
In the low temperature state, after driving the main motor, driving the polygon motor,
In the high temperature state, the main motor is driven after driving the polygon motor, and the preheating mode is shifted to the normal mode when the main motor is driven .   2. The control device according to claim 1, wherein, in the preheating mode, the heat source is turned on and then turned off for a predetermined time from when the print command is received, and thereafter, the control device shifts to the normal mode. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the control device makes the output of the heat source smaller than a maximum value in the normal mode in the preheating mode. A fixing device having a heating member heated by a heat source, a backup member for sandwiching a recording sheet between the heating member, and a temperature sensor for detecting the temperature of the heating member;
A polygon motor for driving a polygon mirror provided in an exposure apparatus that exposes a photoconductor;
A main motor that rotates at least one of the backup member and the heating member;
A control device for controlling the heat source ,
The controller is
When the temperature of the heating member when receiving the print command is in a low temperature state lower than a predetermined temperature , the polygon motor is driven after the main motor is driven,
Wherein when the temperature of the heating member is a high-temperature state is equal to or higher than the predetermined temperature, the image forming apparatus, characterized in that the drive the said main motor after driving the polygon motor when subjected to printing command .

Images